Alcohol use is often assumed to increase sexual risk taking, but empirical evidence for event-level associations is inconsistent. The CHOICES study will examine the co-variation of alcohol use and sexual behavior as they change developmental^ across college and contextually across relationships and situations. Based on a developmental contextual perspective, CHOICES will utilize a longitudinal plus event- based diary design combining longitudinal data across 7 semesters (31/2 years) of college and event-level data across 5 weeks each semester. A multi-ethnic sample of 612 African American, Asian American, European American, and Latino American emerging adult college students will complete a series of web- based surveys. Specific aims are to: (1) Track developmental trajectories of alcohol use, sexual behavior, and their co-variation across college;(2) Model event-level associations between alcohol use and sexual behavior;and (3) Identify person-level (e.g., gender, ethnicity), developmentally-changing (e.g., religiosity, drinking motivations), and contextually-fluctuating (e.g., partner characteristics) predictors of alcohol use, sexual behavior, and their associations. In addition to alcohol use and sexual behaviors, outcomes will include short-term consequences, health events, and academic performance. Analyses will address for whom alcohol use predicts sexual risk taking, under what circumstances, and how this association changes developmentally across the college years. Self-reports from the longitudinal and event-level web surveys will be supplemented by investigator-coded local and campus events and by academic record data through senior year. Open-ended perceptions of change in behavior will be coded to complement the quantitative ... data/Analyses will test predictions from alcohol expectancy models, alcohol myopia theory, and a routine activities perspective on situational deviance using latent growth curve modeling and multi-level models. Alcohol use and sexual behavior are primary causes of morbidity and mortality for adolescents and emerging adults. Pathways taken and lifestyles established during this pivotal period may impact health throughout " adulthood. Little longitudinal research has intensively tracked the alcohol use and sexual behaviors of multi- ethnic samples of emerging adults. The CHOICES study will provide new information about the developmental and situational co-variation of alcohol use and sexual behavior, and the extent to which these links vary by person-level, developmentally-changing, and environmental variables. This examination of whether alcohol use predicts sexual risk taking within an ethnically-diverse sample of college students will inform prevention and policy development by identifying characteristics of students and of situations most at risk for hazardous behaviors.